Higher order discretizations [Enhancement]

[bpfel]

Dear @m-lundberg,

I am currently working on PID control and wondered whether you considered higher order discretizations like a backward Euler or the Tustin/Trapezoidal method. I am not entirely certain how much we might benefit from such an adaptation, but I think your framework is really powerful and neat. Embedding a higher order controller in it would allow an easy comparison of different discretizations.

For an overview of the above mentioned methods consider this webpage.

Please respond if you are interested / still accepting contributions.

Best,

Gianni